time of an outbreak of discolored water during August 1951. Although 

 the water was discolored when the isolation was made, no fish either 

 dead or alive were observed. Bein found that this bacterium was 

 nontoxic to several species of fish. Howell (1953) studied the same 

 outbreak of discolored water. He reported that no great quantity of 

 fish was killed; and that the discoloration was caused by a dino- 

 flagellate, which he described as a new species, Gonyaulax monilata . 



The attempt to determine the minimal lethal concentration of 

 F. piscicida failed since none of the fish died during the experi- 

 mental period. The reason for this lack of toxic effect is not 

 known. Although we followed as nearly as possible the procedures 

 used by Bein (1954)> the experimental conditions employed were 

 unfavorable for the bacterium, especially with regard to toxicity 

 and pigment production. The bacterial counts given in table 10 

 indicate that high concentrations of F, piscicida (orange-pigment- 

 producing bacteria) were present initially. However, the second 

 counts, which were made from samples collected at the end of the 

 5-day experimental period, showed that either this chromogen or 

 its chromogenic characteristic decreased greatly during the inter- 

 vening period. A similar "disappearance" of chromogenic bacteria 

 occurred during the toxicity study with "yellow bacteria" isolated 

 from the unialgal G. brevls cultures. The experimental conditions 

 may have affected the toxieogenic and chromogenic characteristics 

 of this bacteriiun in several possible ways: (l) by killing the 

 organism, (2) by inhibiting the growth of the organism, and (3) by 

 altering the toxieogenic and chromogenic properties of the 

 organism. 



With only initial and terminal counts available the question 

 as to when the "decline" of F. piscicida occurred — either early 

 or gradually during the experimental period — cannot be answered. 

 At no time during the 5-day period did the contents of any con- 

 tainer show the bright orange-yellow discoloration observed by 

 Bein after 2L, hours. The contents of container '}, which received 

 the maximum amount of F. piscicida culture, exhibited a tinge 

 of orange after 24. hours. This slight discoloration gradually 

 became less noticeable and completely disappeared by the fifth 

 day. 



The numbers of F. piscicida recorded in table 10 represent 

 minimal counts, which may be considerably lower than the actual 

 concentrations, because several of the white subsurface colonies 

 produced the characteristic orange pigment after being transferred 

 to agar slants (l^ peptone). All deep orange colonies in plates 

 prepared with samples which contained F. piscicida were considered 

 to have been produced by this species. A few orange colonies 

 appeared in plates prepared from some of the control samples. 



Al 



